1. FIELD OF THE INVENTION
The present invention generally relates to electromagnet door lock devices and more particularly to an improved form of said device which unlocks more rapidly and positively.
2. PRIOR ART
There are various types of electromagnetic door locks, most of which are complicated and expensive to make, install and service and many of which do not perform efficiently or durably. One particular lock is that shown in U.S. Pat. No. 4,487,439. The device utilizes a specially configured electromagnet having a central locking tab which must be perfectly aligned with a central dimple in an armature in order for the device to function properly. Such an electromagnetic device is expensive to make and difficult to properly install. Considerable shear stress is applied to electromagnet housing so that it can rupture and damage the expensive electromagnet.
An improved electromagnet door lock overcoming the foregoing deficiencies is set forth in U.S. Pat. No. 4,826,223, the inventor of which is the present applicant. Although the door lock described and claimed therein works well, in some instances, there is some hesitation and delay in the automatic gravitationally operated door unlocking function when the electromagnet is deenergized. This is because the locking tabs can closely abut the armature, so that the armature cannot freely slide away thereform, urged by gravity.
Additionally, the prior art provides armatures which are rapidly attracted to the electromagnet causing undue noise, rattling and clattering, which is distracting and unwanted noise. This noise is exacerbated by having the armature attracted to the electromagnet at other than a flat, horizontal presentation.
Accordingly, there remains a need for an improvement which will accelerate the rate of separation of the door armature from the electromagnet housing and locking tabs of the device in order to allow the door to be opened more rapidly.